The invention generally relates to turbojet engines and more particularly to a turbojet engine having multiple series of water injection nozzles for injecting streams of atomized water into the airflows entering both a low pressure compressor and a high pressure compressor to reduce NOx emissions, increase thrust and prevent engine performance deterioration.
The focus of point-source emissions regulations has expanded relatively recently from automotive vehicles and electric power generating plants to include almost every device that employs fossil fuel to generate power. These ever more stringent regulations necessitate that both aircraft and turbojet engine manufacturers continually strive to improve the efficiency of their products, as well as decrease their emissions generating capacity. As those skilled in the art will readily understand, however, these two objectives frequently pull relevant design criteria in opposite directions. For example, higher combustion temperatures are generally viewed as assisting a turbojet engine to achieve a relatively high degree of efficiency. High combustion temperatures, however, typically increase the amount of NOx that is produced during combustion by a significant degree.
Previous attempts to increase efficiency and reduce emissions in turbojet engines include ground-based engine wash systems and engine combustor water injection. The ground-based engine wash systems are employed to clean the rotating components of a turbojet engine to thereby obtain a 0.5% to 1.0% increase in fuel efficiency. Such systems, however, are costly to procure and operate, given that an expensive water recovery system is likely needed for capturing the wash effluent and that such systems take aircraft out of service while the turbojet engines are being cleaned.
The older engine combustor water injection systems, which inject water directly into the combustion chamber of a turbojet engine, are known to improve the thrust of a turbojet engine, but typically suffer from draw backs such as an increase in maintenance costs, increased smoke and reduced thermal efficiency.
In one preferred form, the present invention provides a method for reducing NOx emissions while simultaneously increasing the thrust and thermal efficiency on hot days from a turbojet engine. The turbojet engine has a high pressure compressor axially spaced between a low pressure compressor and a turbine. The method includes the steps of: providing a series of water injection nozzles between the low pressure compressor and the high pressure compressor; operating the turbojet engine to produce thrust; operating the series of water injection nozzles to input a finely atomized stream into the high pressure compressor; wherein the stream is comprised of atomized water.
In another preferred form, the present invention provides turbojet engine having an air intake, a compressor, a first series of water injection nozzles and a second series of water injection nozzles. The compressor is coupled to the air intake and receives an inlet flow of air therefrom. The compressor includes a low pressure portion, which compresses the inlet flow, and a high pressure portion, which receives and further compresses the airflow from the low pressure portion. The first series of water injection nozzles is coupled to the air intake and injects a first stream of finely atomized water into the airflow entering the low pressure portion of the compressor. The second series of water injection nozzles is configured to inject a second stream of finely atomized water into the airflow entering the high pressure portion of the compressor.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.